Impact of Assimilating Advanced Himawari Imager Channel 16 Data on Precipitation Prediction over the Haihe River Basin

Hongxiang Ouyang,Zhengkun Qin,Juan Li

doi:10.3390/atmos12101253

Abstract

Assimilation of high-resolution geostationary satellite data is of great value for precise precipitation prediction in regional basins. The operational geostationary satellite imager carried by the Himawari-8 satellite, Advanced Himawari Imager (AHI), has two additional water vapor channels and four other channels compared with its predecessor, MTSAT-2. However, due to the uncertainty in surface parameters, AHI surface-sensitive channels are usually not assimilated over land, except for the three water vapor channels. Previous research showed that the brightness temperature of AHI channel 16 is much more sensitive to the lower-tropospheric temperature than to surface emissivity, which is similar to the three water vapor channels 8–10. As a follow-up work, this paper evaluates the effectiveness of assimilating brightness temperature observations over land from both the three AHI water vapor channels and channel 16 to improve watershed precipitation forecasting through both case analysis (in the Haihe River basin, China) and batch tests. It is found that assimilating AHI channel 16 can improve the upstream near-surface atmospheric temperature forecast, which in turn affects the development of downstream weather systems. The precipitation forecasting test results indicate that adding the terrestrial observations of channel 16 to the assimilation of AHI data can improve short-term precipitation forecasting in the basin.

Highlights

Reliable, timely, and accurate precipitation forecasts are essential for establishing flood forecasting and warning systems, and operational flood forecasting systems require precipitation forecasts several days in advance to predict flood risk [1]
As a follow-up work, this paper evaluates the effectiveness of assimilating brightness temperature observations over land from both the three Advanced Himawari Imager (AHI) water vapor channels and channel 16 to improve watershed precipitation forecasting through both case analysis and batch tests
For precipitation forecasting in small areas over the tropics and mid-latitudes, geostationary satellite observations with high spatial and temporal resolution perfectly meet the need for observations for basin precipitation forecasting

Summary

Introduction

Accurate precipitation forecasts are essential for establishing flood forecasting and warning systems, and operational flood forecasting systems require precipitation forecasts several days in advance to predict flood risk [1]. The impact of assimilating imager data from geostationary satellite on weather forecasting at global and regional scales has been studied extensively [16,17,18,19], and it has been found that assimilating this information can have a positive impact on short- and medium-term water vapor forecasts, effectively improving precipitation forecasts. Some scientists have assimilated AHI data from terrestrial areas, they mainly focused on the three high-altitude water vapor channels; and even though some studies have focused on assimilation techniques for the surface channel, these mostly concentrated on oceanic areas This is mainly due to the influence of surface emissivity. Considering many difficulties in cloud data assimilation, especially the strong uncertainty of O-B characteristics for cloudy data in the land area, this study focuses on the impact of AHI channel 16 assimilation on watershed precipitation in a clear sky.

Data and Experimental Design

Analysis of Results